An air gun is a rifle, pistol, etc., which utilizes a compressed gas to fire a projectile. Air guns may be powered by, for example, a coil spring assembly or a gas spring assembly.
Air guns typically include a compression tube that defines a compression chamber, and is attached to a trigger assembly. A barrel is attached to the compression tube and is in fluid communication with the compression chamber. When powered by a coil spring assembly, the coil spring assembly is housed within the compression chamber of the rifle. The coil spring assembly includes a coil spring coupled to a piston. Cocking the gun moves the piston, which compresses the coil spring until a catch at the rear of the piston engages a sear on the trigger assembly. Actuating the trigger assembly releases the sear of the trigger assembly from the catch, and allows the coil spring to decompress, pushing the piston forward, and thereby compressing the gas, i.e., air, in the compression chamber directly behind the projectile. Once the air pressure rises to a level sufficient to overcome any static friction between the projectile and the barrel, the projectile moves forward within the barrel, propelled by an expanding column of gas.
The coil spring assembly permits use of a center, i.e., an in-line catch, wherein the piston includes a rod that extends along a central, longitudinal axis of the piston. The rod includes the catch which is generally in-line and concentric with a longitudinal axis of the piston. Accordingly, the sear engages the catch substantially in-line with the longitudinal axis of the piston, instead of off-line, radially spaced from the longitudinal axis of the piston, adjacent an outer radial wall of the piston. Such an in-line latching system reduces torque in the spring assembly, which increases the efficiency of the spring assembly and the power of the air gun.
When the air gun is powered by a gas spring assembly, the gas spring assembly is housed within the compression chamber of the rifle. The gas spring assembly includes a piston that defines a sealed interior pressure chamber disposed within the piston. The interior pressure chamber contains a gas, such as air or nitrogen. The piston is slideably disposed over a rod. Cocking the gun moves the piston over the rod, such that the rod displaces the gas within the interior pressure chamber, thereby compressing the gas within the interior pressure chamber, until a catch on the rear of the piston engages the sear on the trigger assembly. Actuating the trigger assembly releases the sear of the trigger assembly and allows the gas spring assembly to decompress, pushing the piston forward, and thereby compressing the gas, i.e., air, in the compression chamber directly behind the projectile. Because the rod is disposed concentric with the piston about the longitudinal axis of the piston, it is difficult to configure an air gun including both an in-line latching system and a gas spring assembly.